Ive been having this problem for a while now... i get the brown algae all over some parts of my sand. I know if i put more water movement it should go away but i just cant seem to have enough? i have 2 power heads, a cpr skimmer/refuge, and a rena filtration system for a 37 gal tank. is this enough? also my refuge seems to get dirty also. How can i keep my tank clean!